From 80bc4a5554226f1f4a14ea204acf1ae2cac6bbb2 Mon Sep 17 00:00:00 2001 From: Max Kazantsev Date: Wed, 5 Jul 2017 06:38:49 +0000 Subject: [PATCH] [IndVars] Canonicalize comparisons between non-negative values and indvars -If there is a IndVar which is known to be non-negative, and there is a value which is also non-negative, then signed and unsigned comparisons between them produce the same result. Both of those can be seen in the same loop. To allow other optimizations to simplify them, we turn all instructions like %c = icmp slt i32 %iv, %b to %c = icmp ult i32 %iv, %b if both %iv and %b are known to be non-negative. Differential Revision: https://reviews.llvm.org/D34979 llvm-svn: 307126 --- llvm/lib/Transforms/Utils/SimplifyIndVar.cpp | 4 ++ llvm/test/Analysis/ScalarEvolution/guards.ll | 6 +-- .../IndVarSimplify/canonicalize-cmp.ll | 52 +++++++++++++++++++ .../IndVarSimplify/eliminate-comparison.ll | 4 +- .../IndVarSimplify/widen-loop-comp.ll | 2 +- 5 files changed, 62 insertions(+), 6 deletions(-) create mode 100644 llvm/test/Transforms/IndVarSimplify/canonicalize-cmp.ll diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp index ec8b0d426265..77f035a5a650 100644 --- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp +++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp @@ -262,6 +262,10 @@ void SimplifyIndvar::eliminateIVComparison(ICmpInst *ICmp, Value *IVOperand) { ICmp->setPredicate(InvariantPredicate); ICmp->setOperand(0, NewLHS); ICmp->setOperand(1, NewRHS); + } else if (ICmpInst::isSigned(Pred) && + SE->isKnownNonNegative(S) && SE->isKnownNonNegative(X)) { + DEBUG(dbgs() << "INDVARS: Turn to unsigned comparison: " << *ICmp << '\n'); + ICmp->setPredicate(ICmpInst::getUnsignedPredicate(Pred)); } else return; diff --git a/llvm/test/Analysis/ScalarEvolution/guards.ll b/llvm/test/Analysis/ScalarEvolution/guards.ll index 52ad4dc73d41..d4b1f431ffc6 100644 --- a/llvm/test/Analysis/ScalarEvolution/guards.ll +++ b/llvm/test/Analysis/ScalarEvolution/guards.ll @@ -19,7 +19,7 @@ entry: loop: ; CHECK: loop: ; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 true) [ "deopt"() ] -; CHECK: %iv.inc.cmp = icmp slt i32 %iv.inc, %len +; CHECK: %iv.inc.cmp = icmp ult i32 %iv.inc, %len ; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 %iv.inc.cmp) [ "deopt"() ] ; CHECK: leave: @@ -41,7 +41,7 @@ leave: define void @test_2(i32 %n, i32* %len_buf) { ; CHECK-LABEL: @test_2( -; CHECK: [[LEN_SEXT:%[^ ]+]] = sext i32 %len to i64 +; CHECK: [[LEN_ZEXT:%[^ ]+]] = zext i32 %len to i64 ; CHECK: br label %loop entry: @@ -52,7 +52,7 @@ loop: ; CHECK: loop: ; CHECK: %indvars.iv = phi i64 [ %indvars.iv.next, %loop ], [ 0, %entry ] ; CHECK: %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1 -; CHECK: %iv.inc.cmp = icmp slt i64 %indvars.iv.next, [[LEN_SEXT]] +; CHECK: %iv.inc.cmp = icmp ult i64 %indvars.iv.next, [[LEN_ZEXT]] ; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 %iv.inc.cmp) [ "deopt"() ] ; CHECK: leave: diff --git a/llvm/test/Transforms/IndVarSimplify/canonicalize-cmp.ll b/llvm/test/Transforms/IndVarSimplify/canonicalize-cmp.ll new file mode 100644 index 000000000000..93dc968af6ab --- /dev/null +++ b/llvm/test/Transforms/IndVarSimplify/canonicalize-cmp.ll @@ -0,0 +1,52 @@ +; RUN: opt -S -indvars < %s | FileCheck %s + +; Check that we replace signed comparisons between non-negative values with +; unsigned comparisons if we can. + +target datalayout = "n8:16:32:64" + +define i32 @test_01(i32 %a, i32 %b, i32* %p) { + +; CHECK-LABEL: @test_01( +; CHECK-NOT: icmp slt +; CHECK: %cmp1 = icmp ult i32 %iv, 100 +; CHECK: %cmp2 = icmp ult i32 %iv, 100 +; CHECK-NOT: %cmp3 +; CHECK: %exitcond = icmp ne i32 %iv.next, 1000 + +entry: + br label %loop.entry + +loop.entry: + %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop.be ] + %cmp1 = icmp slt i32 %iv, 100 + br i1 %cmp1, label %b1, label %b2 + +b1: + store i32 %iv, i32* %p + br label %merge + +b2: + store i32 %a, i32* %p + br label %merge + +merge: + %cmp2 = icmp ult i32 %iv, 100 + br i1 %cmp2, label %b3, label %b4 + +b3: + store i32 %iv, i32* %p + br label %loop.be + +b4: + store i32 %b, i32* %p + br label %loop.be + +loop.be: + %iv.next = add i32 %iv, 1 + %cmp3 = icmp slt i32 %iv.next, 1000 + br i1 %cmp3, label %loop.entry, label %exit + +exit: + ret i32 %iv +} diff --git a/llvm/test/Transforms/IndVarSimplify/eliminate-comparison.ll b/llvm/test/Transforms/IndVarSimplify/eliminate-comparison.ll index 612f01e3cade..a63617e62c0e 100644 --- a/llvm/test/Transforms/IndVarSimplify/eliminate-comparison.ll +++ b/llvm/test/Transforms/IndVarSimplify/eliminate-comparison.ll @@ -111,7 +111,7 @@ return: ; Indvars should not turn the second loop into an infinite one. ; CHECK-LABEL: @func_11( -; CHECK: %tmp5 = icmp slt i32 %__key6.0, 10 +; CHECK: %tmp5 = icmp ult i32 %__key6.0, 10 ; CHECK-NOT: br i1 true, label %noassert68, label %unrolledend define i32 @func_11() nounwind uwtable { @@ -163,7 +163,7 @@ declare void @llvm.trap() noreturn nounwind ; In this case the second loop only has a single iteration, fold the header away ; CHECK-LABEL: @func_12( -; CHECK: %tmp5 = icmp slt i32 %__key6.0, 10 +; CHECK: %tmp5 = icmp ult i32 %__key6.0, 10 ; CHECK: br i1 true, label %noassert68, label %unrolledend define i32 @func_12() nounwind uwtable { entry: diff --git a/llvm/test/Transforms/IndVarSimplify/widen-loop-comp.ll b/llvm/test/Transforms/IndVarSimplify/widen-loop-comp.ll index b87cd0550192..2d24cd732ce8 100644 --- a/llvm/test/Transforms/IndVarSimplify/widen-loop-comp.ll +++ b/llvm/test/Transforms/IndVarSimplify/widen-loop-comp.ll @@ -64,7 +64,7 @@ for.end: ; CHECK-LABEL: @test2 ; CHECK: for.body4.us ; CHECK: %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1 -; CHECK: %cmp2.us = icmp slt i64 +; CHECK: %cmp2.us = icmp ult i64 ; CHECK-NOT: %2 = trunc i64 %indvars.iv.next to i32 ; CHECK-NOT: %cmp2.us = icmp slt i32